The present invention relates to a power transmission joint and, more particularly, to a universal rotational power transmission joint for transmitting torque from a first rotational member to a second rotational member, with a rotational axis of the first rotational member being inclined with respect to the rotational axis of the first rotational member or in parallel to and radially spaced from the first rotational member.
A uniform rotational joint which connects a drive shaft and a driven shaft the axes of which are parallel and eccentric is disclosed in Japanese Patent Laid-Open No. 56-116923/1981.
The joint comprises drive and driven discs each having a through hole at the center, a pipe on a backside thereof and a flat surface on a front side, with an intermediate disc disposed between the drive disc and driven disc so as to be guided by the flat surfaces of the drive and driven discs. The intermediate disc has a hole at the center and a pair of radially slits formed symmetrically with respect to the central hole with a lever passing through the central hole of the intermediate disc. A central portion of the lever is pivotally mounted on the intermediate disc, with the lever having, at both ends thereof, balls which pass through the through holes of the drive and driven discs and are disposed in the pipes whereby an axis of the intermediate disc is disposed on a line passing the axes of the drive and driven discs. A pin has one end secured to the drive disc and the other end inserted in the slit of the intermediate disc and another pin is disposed symmetrically to the previously mentioned pin with respect to the central hole of the intermediate disc, one end of which pin is secured to the driven disc and the other end inserted in the slit of the intermediate disc. When the drive disc is rotated, the rotation is transmitted to the intermediate disc through the pin secured to the drive disc, and the rotation of the intermediate disc is transmitted to the driven disc through the pin secured to the driven disc, whereby the rotation is transmitted from the drive disc to the driven shaft, with uniform rotation.
The conventional joint is not constructed so that the drive shaft smoothly transmits the rotation thereof to the driven shaft with uniform rotation when the rotational axis of the drive disc is inclined against the rotational axis of the driven disc. In such a case, the intermediate disc can not be sufficiently guided by the driven and drive discs so that swinging motion takes place. The pins each comes to contact with an edge of the slit of the intermediate disc, whereby rotation transmission becomes unstable. Noises also take place because of plays due to mechanical wear.
Further, pulsation takes place at a high speed rotation because the rotation transmission between the drive disc and the intermediate disc, and between the intermediate disc and the driven disc is effected by a single pin, whereby rotation balance is destroyed when the discs rotates at a high speed.
Therefore, conditions under which the conventional joint can be utilized are limited and there are problems with respect to power transmission of large torque and high speed rotation, or life of the joint.
Another joint which can be used for a pair of shafts to be connected which are inclined or eccentric with respect to each other is disclosed in Japanese Patent Laid-Open No. 56-46120/1981. The joint comprises a pair of sleeves each fixedly receiving the shaft, annular members each fixed to the sleeve and having sockets formed therein and annularly and equiangularly spaced from each other, balls each movably inserted in the socket and having a through hole, and pins each slidably inserted in the through holes of the balls thereby providing a joint.
An opening, of each of the ball sockets of one of the annular members, positioned at an opposite side to the other annular member is tapered so that inclination of each pin is allowed. The joint can transmit torque or rotation in case the shafts to be connected are inclined to or eccentric to each other, however, the joint can not transmit at a constant velocity rotation. Further, when the rotation is transmitted from one shaft to another, the pins each incline in the rotational direction as well as inclination against rotating axes thereof, and torque or rotation is transmitted through a contact of ball and pin and a contact of pin and the opening portion of the annular member. Thus, the joint is unlikely to smoothly rotate at high speed.